An image sensor is a fundamental component that measures or captures a spatial, frequency and/or intensity distribution of the light to which it is exposed. An example of a system using such a sensor is a digital camera system (irrespective of whether the system captures still or moving images).
The image sensor generally does the following. Impinging light is converted to stored charge (electrons) that are transferred off the pixel area of the image sensor and then converted into voltages (analog signals). The analog signals are then converted into digital values that represent an image to which the image-sensor was exposed.
The charge-coupled device (CCD) remains the most popular technology for implementing an image sensor. A competing technology is the CMOS image sensor. An advantage of a CMOS sensor over the CCD sensor is that pixels on a CMOS sensor are individually addressable such that one or a few of the pixels can be read without having to read all of the pixels. In contrast, CCD imagers according to the Background Art have no provision for individually addressing one or more, but fewer than all, pixels.